Technologies Explained: MICRO SPLINE

11/06/2018

This year we introduced one of the most eagerly awaited groupsets in our history, the XTR M9100 series. One of the highlights of our state-of-the-art mountain bike group is the 12-speed drivetrain. To fit the 12-speed setup our engineers restructured the freehub design with what’s known as MICRO SPLINE technology. In case you haven’t got your head around MICRO SPLINE yet, you can read on for a more detailed explanation.

WHAT IS MICRO SPLINE?

With the arrival of 12-speed cassettes, our engineers had to re-design our freehub to fit the new cassettes and smaller 10 tooth sprocket on the freehub body. That gave us a chance to also look at the way the cassette is mounted on the hub body. We were able to create a stiffer connection with a MICRO SPLINE fitting, which gives 23 equally spaced saw-tooth angled splines for more positive engagement with the cassette. This also allowed our engineers to forge the MICRO SPLINE freehub body from aluminum without risking the deformation and gouging that conventional aluminum cassette bodies suffer.

One important point to note is that the MICRO SPLINE hubs fit all current frames whether you have a boost (148mm) or non-boost (142mm) frame.

So what about compatibility? The MICRO SPLINE freewheels are only compatible with the new XTR M-9100 groupset. This also means that the cassettes of the XTR M-9100 groupset only fit on MICRO SPLINE freehubs, whether they are new 12-speed or new 11-speed. So let’s just spell that out, the new 11-speed M-9100 cassettes only fit on MICRO SPLINE hubs. This is because they have 12-speed spacing and run with a 12-speed chain.